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Friday, February 12, 2016

Ship noise disrupts whale communication

Noise emanating from passing ships may disturb animals such as killer whales and dolphins much more than previously thought, with new research showing that the animals’ communication and ability to find prey could be hampered by the underwater din.

The low rumble of passing ships has long been connected to the disturbance of large whales. But US researchers have documented persistent noise also occurring at medium and higher frequencies, including at 20,000Hz where killer whales, also known as orcas, hear best.

These noise disturbances could be hindering the ability of killer whales to communicate and echolocate – the process of using sound to bounce off objects such as prey and identify where they are. Dolphins and porpoises, which also operate at higher frequencies, may be suffering the same problems.

"The main concern of this is that even a slight increase in sound may make echolocation more difficult for whales," said Scott Veirs of Beamreach, who led the research. "That’s worrying because their prey, chinook salmon, is already quite scarce. Hearing a click off a salmon is probably one of the most challenging things a killer whale does. Hearing that subtle click is harder if there’s a lot of noise around you."

The researchers used underwater microphones to measure the noise created by about 1,600 individual ships as they passed through Haro Strait, in Washington state. The two-year study captured the sound made by 12 different vessel types, including cruise ships, container ships and military vehicles, that passed through the strait about 20 times a day.

For more of The Guardian story: www.theguardian.com